One of the central problems in modern biology is the control of growth at the cellular level and in the whole organism. The somatomedin/insulin-like growth factor peptides are a group of hormonal peptides with strong structural homology to proinsulin. These peptides have been shown to have growth-promoting actions in many different cell types, and it is proposed that they mediate the growth-promoting actions of growth hormone on the whole body. The specific aims of this project are to examine the pathophysiology and interrelations of the somatomedin peptides, and to study the synthesis, mode of transport in plasma, interactions with tissue receptor sites, and their biological actions. The study will utilize radioimmunoassays and radioreceptors, synthetic peptides, synthetic oligonucleotide probes, liquid chromatography, electrophoresis. The long term objectives are to clarify the role of the somatomedin peptides in growth control and to fully understand their actions. This work has health-related importance not only for disorders of human growth in childhood, but in other disease conditions where cellular growth control is disturbed such as neoplasia, diabetes, atherosclerosis and aging.